No HTwo O

I am going to replace the front tires. I did the rears last summer. They will be matched to the rears (brand/model). What size should I get?

PSS9 Suspension.
Speed Line Dayton Wheels
Fronts are 8.5 X 18

Current front tires are 225/40/18 (OEM size)

Rears are 295/30/18 (OEM size is 285/30/18). Not changing these.

Should I stay 225/40/18 or go up one size? What size would that be?

Thanks!

DM993tt

245

Quadcammer

I'd say 235/35/18.

Size wise it works too for the differential

No HTwo O

Dave, 245/??/18.

Need more info.

No HTwo O

Oliver, not 235/40/18??

The rears keep the OEM aspect ratio of 30 while going up from 285 to 295.

Quadcammer

You're absolutely right, my mistake.

235/40/18s is what I run up front

AnthonySp

I have 8x18 bbs rs-gt wheels up front and run 235/40/18 mpsc and really love the extra sidewall of the "40". I have a pss-10 on my car.

No HTwo O

OK, thanks guys, so a 235/40/18 vs the OEM 225/40/18 is just slightly "taller" and a little wider "footprint"?

wagongotya

235/40/18 sir

No HTwo O

Yes, Captain my Captain!

Have a great weekend.

malcolmd

Wieghted tyre diameter for "Generic" tyres

8" Rim
225/40/18 = 25.1"
235/40/18 = 25.4"

8.5" Rim
245/40/15 = 25.7"
245/35/18 = 24.8"
255/35/18 = 25.0"

9" Rim
265/35/18 = 25.3"

10" Rim
285/30/18 = 24.7"
295/30/18 = 25.0"

11" Rim
305/30/18 = 25.2"
315/30/18 = 25.4"

Bear in mind some individual manufacturer's tyres do vary from this generic sizing , so take your existing rear choice into consideration as well as the fact that that tyre might not come in every config.

Generally speaking, as you are committed to keeping 295/30/18 at rear, your best match would indeed be 235/40/18 or perhaps 245/35/18's although these would be better with 305/30/18s at rear.

Personally, I'd go with 255/35/18s on 8.5-9" rims and 315/30/18s on 11.0" rims.

No HTwo O

Thanks for the help, everyone. I ordered the 235/40/18's last night from Tire Rack. Tires will arrive Tuesday. Then off to the dealership (only time I ever use the dealerships anymore) for mounting and balancing Friday. Hope to "scrub" them in a little bit before my novice DE at Road America 5/27 - 5/29!

ronnie993tt

So 235 and 295 is as big as you can go on the stock rims without clearance issues? If so why do they not use the larger sizes from the factory?

Basal Skull

You'd get a little bulging of the side walls with the stock rims if you put larger tires on them, not as good for performance. Those sizes were already pretty big back in 1997.

malcolmd

It is not a clearance issue, it relates to how the tyre/sidewall will perform and how safe the fitting (bead to rim) will be.

Clearance relates to the combination of tyre diameter/height, shoulder geometry/shape, section width, ride height and rim offset. Rim width with correct offset has little indepentant effect unless extreme.